Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The PCM monitors the rich-to-lean and lean-to-rich transition time. A transition is defined as the following:
The HO2S voltage changes from above 625 mV to below 325 mV or from below 325 mV to above 625 mV. If the PCM detects that the difference between the rich-to-lean average transition time and the lean-to-rich average transition time is more than a specified value, DTC P1134 will set for bank 1 sensor 1 or DTC P1154 will set for bank 2 sensor 1.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P1134 HO2S Transition Time Ratio Bank 1 Sensor 1 |
| • | DTC P1154 HO2S Transition Time Ratio Bank 2 Sensor 1 |
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0201-P0208, P0300, P0301-P0308, P0410, P0412, P0418, P0419, P0442, P0443, P0446, P0449, P0455, P1133, P1153 are not set. |
| • | The system voltage is between 10-18 volts. |
| • | The Engine Speed parameter is between 1,200-2,300 RPM. |
| • | The MAF Sensor parameter is between 15-30 g/s. |
| • | The TP Sensor parameter is more than 3.5 percent. |
| • | The ECT Sensor parameter is more than 70°C (158°F). |
| • | The Loop Status parameter is closed. |
| • | The transmission is not in Park, Reverse, or Neutral. |
| • | DTCs P1134 and P1154 run once per key cycle once the above conditions are met for 3 seconds. |
Conditions for Setting the DTC
The PCM detects that the difference between the average rich-to-lean and lean-to-rich transition times, during an 65 second monitoring period, is greater than 90 ms.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||||
2 |
Does the voltage fluctuate rapidly above and below the specified range? | 350-500 mV | Go to Step 3 | Go to Step 4 | ||||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||
4 |
Is the voltage within the specified range? | 400-500 mV | Go to Step 5 | Go to Step 6 | ||||||||||||
5 |
Is the voltage less than the specified value? | 25 mV | Go to Step 8 | Go to Step 7 | ||||||||||||
6 | Test the affected HO2S 1 high signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||||||||
7 | Test the affected HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||||||||
8 | Inspect for the following that may affect the HO2S operation: Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||||||||||
9 | Test for an intermittent and for a poor connection at the affected HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||||||
10 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||||||
11 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
12 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 | ||||||||||||
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||||||
